This invention relates to an operation microscope for use in ophthalmic and surgical operations and more particularly to a microscope for use in surgical operations in which two observation rays entering respectively to the left and right eyes of an operator and illumination rays pass through a single objective lens.
Especially in microscopes for use in surgical operations in ophthalmology and otorhinology it is preferable to so construct the microscope that the illumination rays and the observation rays cross each other at the smallest possible angle in order to illuminate deep parts of the diseased tissue. For example, using a microscope to confirm whether or not a part of the lens of an eye remains in the capsula lentis after the removal of the lens in a cataract operation, it is impossible to reliably confirm the presence or absence of any remaining part of the lens by illuminating the lens and the capsula lentis from the front side thereof, since both the lens and the capsula lentis are transparent. Accordingly, it has been the usual practice to confirming whether any part of the lens remains by illuminating the fundus through the capsula lentis so that rays reflected by the fundus pass through the capsula lentis from the back side thereof.
In such confirming work, it is impossible to sufficiently illuminate the fundus because of interruption by the pupil if the optical axis of the observation optical system and the optical axis of the illumination optical system cross each other at a large angle, and therefore it is very difficult to reliably confirm whether any part of the lens remains in the capsula lentis.
Taking the circumstances mentioned above into consideration, there has heretofore been proposed a microscope for use in surgical operation wherein the illumination rays enter a single objective lens in parallel with the optical axis of the single objective lens at a point perpendicularly offset from the center point of a line connecting the points of incidence of two observation beams, whereby the illumination rays are refracted by the single objective lens are directed to the focal point of the single objective lens.
However, this prior art microscope in which the illumination rays enter the single objective lens at the periphery thereof, has a problem in that it is impossible to sufficiently illuminate deep parts of the diseased tissue because of misalignment of the optical axes of the observation rays and the illumination rays.